Hurricane DALILA

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HURRICANE DALILA DISCUSSION NUMBER 14
NWS NATIONAL HURRICANE CENTER MIAMI FL EP042013
800 PM PDT TUE JUL 02 2013
THE CLOUD PATTERN OF DALILA HAS CHANGED LITTLE IN ORGANIZATION
DURING THE LAST SEVERAL HOURS...WITH THE CYCLONE STILL MAINTAINING A
SMALL AND FAIRLY SYMMETRIC CDO. A 0016 UTC SSMI/S PASS DID...
HOWEVER...SHOW A SLIGHT DEGRADATION OF THE INNER CORE...WITH THE
EYEWALL OPEN TO THE EAST. THE MID-LEVEL CENTER ALSO WAS DISPLACED
NORTHWEST OF THE LOW-LEVEL CENTER...SUGGESTING THAT SOUTHEASTERLY
SHEAR IS STILL AFFECTING THE CYCLONE. THE INITIAL INTENSITY IS KEPT
AT 65 KT IN AGREEMENT WITH A TAFB DVORAK INTENSITY ESTIMATE OF
T4.0/65 KT.
THE STATISTICAL MODEL GUIDANCE SHOWS DALILA CHANGING LITTLE IN
STRENGTH DURING THE NEXT 2-3 DAYS...EVEN THOUGH THE HURRICANE
SHOULD BE PASSING OVER RELATIVELY WARM WATERS. THE MAIN OBSTACLE TO
ANY FURTHER STRENGTHENING IS LIKELY RELATED TO MODERATE EAST-
SOUTHEASTERLY TO SOUTHEASTERLY WIND SHEAR FORECAST TO PREVAIL OVER
THE CYCLONE. THE ECMWF SHOWS DALILA QUICKLY WEAKENING AS A RESULT
OF THE ENTRAINMENT OF A LAYER OF DRY AIR TO THE WEST OF DALILA. IT
IS DIFFICULT...HOWEVER...TO IMAGINE THIS SCENARIO...GIVEN THAT THE
UPPER-LEVEL FLOW IS FROM THE EAST. THE NHC INTENSITY FORECAST
CONTINUES TO LEAN ON THE GFS-BASED MODEL GUIDANCE AND IS NEAR A
BLEND OF THE SHIPS/LGEM THROUGH 72 HOURS...AND THEN NEAR THE
MULTI-MODEL INTENSITY CONSENSUS AIDS BEYOND THAT TIME.
DALILA IS NOT MOVING MUCH. A LONG-TERM AVERAGE OF SATELLITE FIXES
YIELDS A HIGHLY UNCERTAIN INITIAL MOTION ESTIMATE OF 270/02.
HOWEVER...RECENT MICROWAVE FIXES SUGGEST THAT A WEST-SOUTHWESTWARD
TO SOUTHWESTWARD DRIFT MAY HAVE COMMENCED. A MID-LEVEL TROUGH ACROSS
NORTHERN MEXICO HAS TEMPORARILY WEAKENED THE SUBTROPICAL RIDGE AND
CREATED A WEAK STEERING ENVIRONMENT OVER THE CYCLONE. HOWEVER...THE
STRONG HEAT RIDGE OVER THE WESTERN UNITED STATES IS FORECAST TO MOVE
SOUTHEASTWARD DURING THE NEXT COUPLE OF DAYS...WHICH SHOULD CAUSE
DALILA TO TURN SOUTH OF WEST WITH SOME MINOR INCREASE IN FORWARD
SPEED. THE TRACK GUIDANCE REMAINS DIVERSE...WITH THE ECMWF STILL
FORECASTING A WEAK CYCLONE MOVING SOUTHWARD AND DISSIPATING. THE
GFS CONTINUES TO SHOW A STRONGER SYSTEM MOVING ON A MORE WESTERLY
TRACK. THE NEW NHC TRACK FORECAST CONTINUES TO WEIGH THE GFS
SOLUTION MORE...AND IS BETWEEN THE PREVIOUS FORECAST AND THE
MULTI-MODEL CONSENSUS TVCE THROUGH 72 HOURS...AND CLOSER TO THE GFS
LATE IN THE PERIOD.
FORECAST POSITIONS AND MAX WINDS
INIT 03/0300Z 18.3N 107.3W 65 KT 75 MPH
12H 03/1200Z 18.1N 107.6W 65 KT 75 MPH
24H 04/0000Z 17.7N 108.2W 65 KT 75 MPH
36H 04/1200Z 17.4N 108.9W 65 KT 75 MPH
48H 05/0000Z 17.4N 109.9W 60 KT 70 MPH
72H 06/0000Z 17.6N 111.9W 55 KT 65 MPH
96H 07/0000Z 18.0N 114.0W 40 KT 45 MPH
120H 08/0000Z 18.5N 116.5W 30 KT 35 MPH...POST-TROP/REMNT LOW
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FORECASTER KIMBERLAIN
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